ＲＯＳ（六）：使用smartcar进行仿真

如果小伙伴们按照ＲＯＳ（五）的博客走过一遍的话，使用ｓｍａrtcar进行仿真应该差不多．

按照之前的教程，下面两步可省略：
1.安装urdf_tutorial

sudo apt-get install ros-indigo-urdf-tutorial

安装liburdfdom-tools，提供对urdf文件的检查

sudo apt-get install liburdfdom-tools

我们可以从官方的文档中发现，ＲＯＳ是有很多版本的，ＲＯＳ对ｕｒｄｆ的文件的支持可能不是很好，这时使用宏定义的.xacro文件兼容性更好，扩展性也更好．　所以可以把（五）中的一整个ｕｒｄｆ文件重新整理成三个.xacro文件

３．机器人主题部分smartcar_body.urdf.xacro

  
<robot name="smartcar" xmlns:xacro="http://ros.org/wiki/xacro">  <xacro:property name="M_PI" value="3.14159"/>      <xacro:include filename="$(find smartcar_description)/urdf/gazebo.urdf.xacro"/>  <xacro:property name="base_x" value="0.33" />  <xacro:property name="base_y" value="0.33" />  <xacro:macro name="smartcar_body">  <link name="base_link">  <inertial>  <origin xyz="0 0 0.055"/>  <mass value="1.0" />  <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>  inertial>  <visual>  <geometry>  <box size="0.25 .16 .05"/>  geometry>  <origin rpy="0 0 0" xyz="0 0 0.055"/> <material name="blue">  <color rgba="0 0 .8 1"/>  material>  visual>  <collision>  <origin rpy="0 0 0" xyz="0 0 0.055"/>  <geometry>  <box size="0.25 .16 .05" />  geometry>  collision>  link>  <link name="left_front_wheel">  <inertial>  <origin  xyz="0.08 0.08 0.025"/>  <mass value="0.1" />  <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>  inertial>  <visual>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  <material name="black">  <color rgba="0 0 0 1"/>  material>  visual>  <collision>  <origin rpy="0 1.57075 1.57075" xyz="0.08 0.08 0.025"/>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  collision>  link>  <joint name="left_front_wheel_joint" type="continuous">  <axis xyz="0 0 1"/>  <parent link="base_link"/>  <child link="left_front_wheel"/>  <origin rpy="0 1.57075 1.57075" xyz="0.08 0.08 0.025"/>  <limit effort="100" velocity="100"/>  <joint_properties damping="0.0" friction="0.0"/>  joint>  <link name="right_front_wheel">  <inertial>  <origin xyz="0.08 -0.08 0.025"/>  <mass value="0.1" />  <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>  inertial>  <visual>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  <material name="black">  <color rgba="0 0 0 1"/>  material>  visual>  <collision>  <origin rpy="0 1.57075 1.57075" xyz="0.08 -0.08 0.025"/>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  collision>  link>  <joint name="right_front_wheel_joint" type="continuous">  <axis xyz="0 0 1"/>  <parent link="base_link"/>  <child link="right_front_wheel"/>  <origin rpy="0 1.57075 1.57075" xyz="0.08 -0.08 0.025"/>  <limit effort="100" velocity="100"/>  <joint_properties damping="0.0" friction="0.0"/>  joint>  <link name="left_back_wheel">  <inertial>  <origin xyz="-0.08 0.08 0.025"/>  <mass value="0.1" />  <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>  inertial>  <visual>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  <material name="black">  <color rgba="0 0 0 1"/>  material>  visual>  <collision>  <origin rpy="0 1.57075 1.57075" xyz="-0.08 0.08 0.025"/>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  collision>  link>  <joint name="left_back_wheel_joint" type="continuous">  <axis xyz="0 0 1"/>  <parent link="base_link"/>  <child link="left_back_wheel"/>  <origin rpy="0 1.57075 1.57075" xyz="-0.08 0.08 0.025"/>  <limit effort="100" velocity="100"/>  <joint_properties damping="0.0" friction="0.0"/>  joint>  <link name="right_back_wheel">  <inertial>  <origin xyz="-0.08 -0.08 0.025"/>  <mass value="0.1" />  <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>  inertial>  <visual>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  <material name="black">  <color rgba="0 0 0 1"/>  material>  visual>  <collision>  <origin rpy="0 1.57075 1.57075" xyz="-0.08 -0.08 0.025"/>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  collision>  link>  <joint name="right_back_wheel_joint" type="continuous">  <axis xyz="0 0 1"/>  <parent link="base_link"/>  <child link="right_back_wheel"/>  <origin rpy="0 1.57075 1.57075" xyz="-0.08 -0.08 0.025"/>  <limit effort="100" velocity="100"/>  <joint_properties damping="0.0" friction="0.0"/>  joint>  <link name="head">  <inertial>  <origin xyz="0.08 0 0.08"/>  <mass value="0.1" />  <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>  inertial>  <visual>  <geometry>  <box size=".02 .03 .03"/>  geometry>  <material name="white">  <color rgba="1 1 1 1"/>  material>  visual>  <collision>  <origin xyz="0.08 0 0.08"/>  <geometry>  <cylinder length=".02" radius="0.025"/>  geometry>  collision>  link>  <joint name="tobox" type="fixed">  <parent link="base_link"/>  <child link="head"/>  <origin xyz="0.08 0 0.08"/>  joint>  xacro:macro>  robot>

４．gazebo属性部分 gazebo.urdf.xacro

  
<robot xmlns:controller="http://playerstage.sourceforge.net/gazebo/xmlschema/#controller"   xmlns:interface="http://playerstage.sourceforge.net/gazebo/xmlschema/#interface"   xmlns:sensor="http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor"   xmlns:xacro="http://ros.org/wiki/xacro"   name="smartcar_gazebo">      <xacro:macro name="smartcar_sim">  <gazebo reference="base_link">  <material>Gazebo/Bluematerial>  gazebo>  <gazebo reference="right_front_wheel">  <material>Gazebo/FlatBlackmaterial>  gazebo>  <gazebo reference="right_back_wheel">  <material>Gazebo/FlatBlackmaterial>  gazebo>  <gazebo reference="left_front_wheel">  <material>Gazebo/FlatBlackmaterial>  gazebo>  <gazebo reference="left_back_wheel">  <material>Gazebo/FlatBlackmaterial>  gazebo>  <gazebo reference="head">  <material>Gazebo/Whitematerial>  gazebo>  xacro:macro>  robot>

５．主文件 smartcar.urdf.xacro

  
<robot name="smartcar"    xmlns:xi="http://www.w3.org/2001/XInclude"  xmlns:gazebo="http://playerstage.sourceforge.net/gazebo/xmlschema/#gz"  xmlns:model="http://playerstage.sourceforge.net/gazebo/xmlschema/#model"  xmlns:sensor="http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor"  xmlns:body="http://playerstage.sourceforge.net/gazebo/xmlschema/#body"  xmlns:geom="http://playerstage.sourceforge.net/gazebo/xmlschema/#geom"  xmlns:joint="http://playerstage.sourceforge.net/gazebo/xmlschema/#joint"  xmlns:controller="http://playerstage.sourceforge.net/gazebo/xmlschema/#controller"  xmlns:interface="http://playerstage.sourceforge.net/gazebo/xmlschema/#interface"  xmlns:rendering="http://playerstage.sourceforge.net/gazebo/xmlschema/#rendering"  xmlns:renderable="http://playerstage.sourceforge.net/gazebo/xmlschema/#renderable"  xmlns:physics="http://playerstage.sourceforge.net/gazebo/xmlschema/#physics"  xmlns:xacro="http://ros.org/wiki/xacro">  <xacro:include filename="$(find smartcar_description)/urdf/smartcar_body.urdf.xacro" />    <smartcar_body/>  <smartcar_sim/>  
robot>

６．lanuch文件smartcar_display.rviz.launch

<launch>  <param name="/use_sim_time" value="false" />    <arg name="urdf_file" default="$(find xacro)/xacro.py '$(find smartcar_description)/urdf/smartcar.urdf.xacro'" />  <arg name="gui" default="false" />  <param name="robot_description" command="$(arg urdf_file)" />  <param name="use_gui" value="$(arg gui)"/>  <node name="arbotix" pkg="arbotix_python" type="arbotix_driver" output="screen">  <rosparam file="$(find smartcar_description)/config/smartcar_arbotix.yaml" command="load" /> <param name="sim" value="true"/>  node>  <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher" >  node>  <node name="robot_state_publisher" pkg="robot_state_publisher" type="state_publisher">  <param name="publish_frequency" type="double" value="20.0" />  node>    <node pkg="tf" type="static_transform_publisher" name="odom_left_wheel_broadcaster" args="0 0 0 0 0 0 /base_link /left_front_link 100" />  <node pkg="tf" type="static_transform_publisher" name="odom_right_wheel_broadcaster" args="0 0 0 0 0 0 /base_link /right_front_link 100" />  <node name="rviz" pkg="rviz" type="rviz" args="-d $(find smartcar_description)/urdf.rviz" />  launch>

７．编译工作空间并运行

cd ~/catkin_ws/src/smartcar_description
//注意最后面的点
cp /opt/ros/indigo/share/urdf_tutorial/rviz/urdf.rviz  .

８．在indigo版本里，新增smartcar_description/config/smartcar_arbotix.yaml文件，内容为：

port: /dev/ttyUSB0
baud: 115200
rate: 20
sync_write: True
sync_read: True
read_rate: 20
write_rate: 20controllers: {#  Pololu motors: 1856 cpr = 0.3888105m travel = 4773 ticks per meter (empirical: 4100)base_controller: {type: diff_controller, base_frame_id: base_link, base_width: 0.26, ticks_meter: 4100, Kp: 12, Kd: 12, Ki: 0, Ko: 50, accel_limit: 1.0 }
}

９．编译完后进行仿真实验

ｒｏｓｃｏｒｅ
//新终端
．　ｄｅvel/setup.bash
roslaunch smartcar_description smartcar_display.rviz.launch

打开如上图所示，ＬＺ为看美观，把名字都隐藏起来．然后发布一个ｍｅｓｓａｇｅ，让小车旋转起来：

rostopic pub -r 10 /cmd_vel geometry_msgs/Twist '{linear: {x: 0.5, y: 0, z: 0}, angular: {x: 0, y: 0, z: 0.5}}'

小车就能进行旋转了！
使用rqt_graph可以看到具体的节点关系

rqt_graph

参考链接：
http://wiki.ros.org/xacro
https://www.ncnynl.com/archives/201609/843.html

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